This invention relates to functionalized diene monomers, polymers containing functionalized dienes, and methods for preparing functional or polar group-bearing diene monomers and polymers.
Interest in the field of functionalized polymeric materials stems from the desire to combine the unique properties of a functional group with those of a high molecular weight polymer.
Functionalized polymers have the potential for crosslinking via ionic interactions and covalent bonds, leading to improved properties for applications such as polymer blends. The introduction of specifically interacting groups is a particularly versatile route to miscibility enhancement. Other applications of these materials are in membranes, packaging, dispersants, adhesives and coatings. In addition, functionalized polymers may be used in the modification of existing materials to alter their adhesion, processability, solubility, dyeability, thermal, mechanical, and other properties.
Functional groups can be introduced into a polymer by two general approaches: (1) chemical modification of a nonfunctionalized, preformed polymer, or (2) polymerization or copolymerization of monomers containing the functionality. The second method has the advantages of producing a more homogeneous polymer with more uniform functionalization, the ability to analyze the monomers prior to polymerization, and the ability to control loading and distribution of functional groups along the polymer backbone.
A number of different functional or other polar groups have been incorporated into various polyolefin and polyvinyl materials. Successful functionalization is typically performed after polymer formation. In many instances, only terminal functionalization is achieved. Where functionalized monomers have been polymerized to prepare functional group-bearing polymers, the extra steps of masking the monomer functionality prior to polymerization, and then subsequently removing the mask, have been required. Limited success has previously been achieved in the polymerization of functionalized diene monomers, although such monomers have enormous commercial significance and utility in materials such as elastomers, adhesives, sealants, coatings, molded mechanical articles, and the like.
Initial work with nonsilicon-containing functionalized dienes was reported by Petzhold et al., which focused on anionic polymerization of N,N-diethylaminoisoprene and elucidation of microstructures. Petzhold, C., et al. (Makromol. Chem., Rapid Commun 1993, 14, 33-43) refers to low yields ( less than 50%) of low molecular weight (number-average molecular weight 5,000 g/mol) polymers obtained by anionic and radical polymerization of 2-(N,N-disopropyl-aminomethyl)-1,3-butadiene. Petzhold, C., et al. (Macromolecules 1994, 27, 3707-13) refers to low yields of low molecular weight polymers obtained by anionic polymerization of a series of 2-(N,N-dialkylaminomethyl)-1,3-butadienes.
What is needed are new functionalized diene monomers and methods for preparing and polymerizing functionalized dienes to produce high yields of functionalized diene polymers, without the requirements of masking and unmasking the functional group, or of adding the functionality only after polymerization.
The present invention provides functionalized diene monomers and methods for preparing and polymerizing such functional group-bearing monomers to prepare high yields of functionalized polymers and copolymers.
The diene monomers and functionalized polymers of the invention include, but are not limited to, butadiene monomers and polymerized functionalized butadiene monomers such as: 2-(N,N-dimethylaminomethyl)-1,3-butadiene (Compound 1a), 2-(N N-diethylaminomethyl)-1,3-butadiene (Compound 1b), 2-(N,N-di-n-propylaminomethyl)-1,3-butadiene (Compound 1c), 2-(cyanomethyl)-1,3-butadiene (Compound 2), 2-(aminomethyl)-1,3-butadiene (Compound 3), 2-(hydroxymethyl)-1,3-butadiene (Compound 4), 2-(carboxymethyl)-1,3-butadiene (Compound 5), 2-(acetoxymethyl)-1,3-butadiene (Compound 6), 2-(2-alkoxy-2-oxoethyl)-1,3-butadiene (Compound 7), as well as disubstituted functionalized diene monomers and polymerized disubstituted functionalized diene monomers such as 2,3-bis(cyanomethyl)-1,3-butadiene (Compound 8), 2,3-bis(dialkylaminomethyl)-1,3-butadiene (Compound 9), 2,3-bis(4-ethoxy-4-oxobutyl)-1,3-butadiene (Compound 10) and the 2,3-bis(3-cyanopropyl)-1,3-butadiene (Compound 11). Also provided herein are methods for synthesizing these and other functionalized diene monomers, polymers, and copolymers.
The resulting polymers and copolymers may be used as is or blended with other materials to make a variety of new products, including adhesives, sealants, surfactants, elastomers, ionomers for, e.g., coatings and membranes, and may also be employed as functionalized polyolefin precursors. The resulting functionalized polymers or polymer blends may be quaternized, hydrogenated, cross-linked, or subject to other known polymer reactions to enhance properties for specific applications, as described in detail herein.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention will be attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
Reference will now be made in detail to the presently preferred embodiments of the invention, which together with the following examples, serve to explain the principles of the invention.
The present invention provides functionalized diene monomers of the formula: 
Compound 1: Yxe2x95x90NR2 (1a: R=methyl; 1b: R=ethyl; 1c: R=n-propyl)
Compound 2: Yxe2x95x90CN
Compound 3: Yxe2x95x90NH2 
Compound 4: Yxe2x95x90OH
Compound 5: Yxe2x95x90COOH
Compound 6: Yxe2x95x90OCOCH3 
Compound 7: Yxe2x95x90COOR (R=any alkyl group)
and similar functionalized monomers, having various functional groups, which may be synthesized by following the teachings provided herein.
The present invention also provides disubstituted functionalized diene monomers of the formula: 
Compound 8: Yxe2x95x90CN
Compound 9: Yxe2x95x90NR2 (9a: R=methyl; 9b: R=ethyl; 9c: R=n-propyl)
and similar disubstituted functionalized diene monomers, having various functional groups, which may be synthesized by following the teachings provided herein.
The invention further provides disubstituted functionalized diene monomers of the formula: 
Compound 10: Yxe2x95x90COOEt
Compound 11: Yxe2x95x90CN
and similar disubstituted functionalized monomers, having various functional groups, all of which may be synthesized by one of ordinary skill in the art given the teachings provided herein.
Compounds 1-9 and similar functionalized diene monomers are preferably synthesized by the techniques discussed below, although any suitable method may be used. The invention, including the polymers and polymerization products and processes of the invention, should be understood as not being limited to the following preferred monomers or monomer syntheses.
Compounds 1, 2, 3, 4 and 6 can be synthesized from the monobromide precursor, 2-(bromomethyl)-1,3-butadiene in several ways. Two methods are described below for the synthesis of the monobromide. The second method gives improved yields and purity.
The first method for the synthesis of 2-(bromomethyl)-1,3-butadiene involves the synthesis of 1,4-dibromo-2-methyl-2-butene by reacting isoprene with bromine at a temperature in the range of about 20xc2x0 C. or below. The dibromide may then be reacted at elevated temperature in the range of about 120xc2x0 C. with 1,3-dimethyl-3,4,5-6-tetrahydro-2(1H)-pyrimidinone (DMPU). The resulting 2-(bromomethyl)-1,3-butadiene is then reacted with the desired dialkylamine, sodium cyanide, phthalamide then hydrazine, potassium acetate then base, and potassium acetate to give 1, 2, 3, 4 and 6, respectively.
The second method for the synthesis of 2-(bromomethyl)-1,3-butadiene is preferred as it leads to higher yields of higher purity functionalized dienes. It involves the synthesis of a cyclic sulfone, 3-methyl-2,5-dihydrothiophene-1,1-dioxide, via reaction of isoprene with sulfur dioxide. This sulfone is a solid and allows for purification by recrystallization. The sulfone is then reacted with NBS to give the monobromide, 3-bromomethyl-2,5-dihydrothiophene-1,1-dioxide. Upon heating the monobromide, SO2 is released and pure 2-(bromomethyl)-1,3-butadiene is produced. The monobromide is allowed to react in the same way with various compounds as described above to give 1, 2, 3, 4 and 6.
Although it is possible to synthesize Compounds 5 and 7 from the monobromide precursor route, 5 and 7 were made differently as described below. To synthesize 5, isoprene was reacted with potassium t-butoxide then butyl lithium followed by carbon dioxide. Compound 7 is readily obtained from Compound 5 by refluxing with an alcohol.
Compounds 8 and 9 are obtained by the second precursor route with one change, the starting material is changed from isoprene to 2,3-(dimethyl)-1,3-butadiene. The 2,3-(dibromomethyl)-1,3-butadiene precursor can be reacted with a number of nucleophiles including those listed above to give difunctionalized dienes. To obtain 8 and 9, the dibromo precursor is reacted with sodium cyanide or a dialkylamine, respectively.
Compounds 10 and 11 are synthesized by a route differing from 1-9. Compound 10 is preferably synthesized by mixing ethyl4-chlorobutyrate with acetone and sodium iodide. 1,2-dibromomethane is then mixed with zinc granules and THF. Chlorotrimethylsilane is then added to this mixture. Subsequently, the ethyl-4-iodobutyrate mixture is added and the mix is heated to about 50xc2x0 C. Lithium chloride and copper cyanide are then added. The solution is warmed to about 0xc2x0 C. and then cooled to about xe2x88x9278xc2x0 C. or less, and 1,4-dichlorobutyne is added. The reaction is then quenched and the organic layer is extracted, dried and filtered. Varying diester derivatives of Compound 10 may be synthesized in a similar manner by varying the alkyl-4-haloester added to acetone and sodium iodide.
Compound 11 is preferably synthesized in the same manner as indicated above with respect to Compound 10, except that the synthesis starts with 4-chlorobutyronitrile instead of ethyl-4-chlorobutyrate. Again, any cyano monomer can be prepared by varying the 4-halonitrile.
Accordingly, the monomers and polymers according to the present invention are not limited to the preferred compounds, Compounds 1a-c, 2, 3, 4, 5, 6, 7, 8, 9a-c, 10, and 11, but also extend to other aminoisoprenes, diester derivatives, cyano monomers, and other functionalized diene monomers and polymers that can be prepared given the detailed description of the preferred product and process embodiments provided herein.
According to this invention, polymerization and recovery of polymer are suitably carried out according to various methods suitable for diene monomer polymerization processes. This includes batchwise, semi-batchwise or continuous operations under conditions that exclude air and other atmospheric impurities, particularly moisture. The polymerization of the functionalized monomers of the invention may also be carried out in a number of different polymerization reactor systems, including but not limited to bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and precipitation polymerization systems. The currently preferred methods are solution, bulk and emulsion polymerizations.
The polymerization reaction may use a free radical redox initiator, although anionic, cationic, and catalytic initiation systems may also be employed. The preferred initiation systems are free radical and anionic, depending upon the particular monomers being polymerized. An advantage of free radical polymerization is that reactions can typically be carried out under less rigorous conditions than ionic polymerizations. Free radical initiation systems also exhibit a greater tolerance of trace impurities.
Examples of free radical initiators that are useful in the practice of the present invention are those known as xe2x80x9credoxxe2x80x9d initiators, such as combinations of chelated iron salts, sodium formaldehyde sulfoxylate, and organic hydroperoxides. Representative of organic hydroperoxides are cumene hydroperoxide, paramenthane hydroperoxide, and tertiary butyl hydroperoxide. Tertiary butyl hydroperoxide (t-BHP), tertiary butyl peracetate (t-BPA) and xe2x80x9cazoxe2x80x9d initiators, such as azobisiobutyronitrile (AIBN), are preferred.
The reaction temperature is typically maintained in the range of between 0 and 150xc2x0 C. Temperatures between about 70 and 120xc2x0 C. are generally preferred. The reaction pressure is not critical. It is typically only sufficiently high to maintain liquid phase reaction conditions; it may be autogenic pressure, which will vary depending upon the components of the reaction mixture and the temperature, or it may be higher, e.g., up to 1000 p.s.i. High pressures are suitably obtained by pressuring with an inert gas.
In batch operations, the polymerization time of functionalized diene monomers can be varied as desired; it may vary, for example, from a few minutes to several days. Polymerization in batch processes may be terminated when monomer is no longer absorbed, or earlier, if desired, e.g., if the reaction mixture becomes too viscous. In continuous operations, the polymerization mixture may be passed through a reactor of any suitable design. The polymerization reactions in such cases are suitably adjusted by varying the residence time. Residence times vary with the type of reactor system and range, for example, from 10 to 15 minutes to 24 or more hours.
The concentration of monomer in the reaction mixture may vary upward from 5 percent by weight of the reaction mixture, depending on the conditions employed; the range from 20 to 80 percent by weight is preferred.
The polymerization reactions according to this invention may be carried out in a suitable solvent which is liquid under the conditions of reaction and relatively inert. The solvent may have the same number of carbon atoms per molecule as the diene reactant or it may be in a different boiling range. Preferred as solvents are alkane and cycloalkane hydrocarbons. Suitable solvents are, for example, hexane, cyclohexane, methylcyclohexane, or various saturated hydrocarbon mixtures. Aromatic hydrocarbons such as benzene, toluene, isopropylbenzene, xylene, or halogenated aromatic compounds such as chlorobenzene, bromobenzene, or orthodichlorobenzene may also be employed. Other useful solvents include tetrahydrofuran and dioxane.
Conventional emulsion recipes may also be employed with the present invention; however, some restrictions and modifications may arise either from the polymerizable monomer itself, or the polymerization parameters. Ionic surfactants, known in the art, including sulfonate detergents and carboxylate, sulfate, and phosphate soaps are useful in this invention. The level of ionic surfactant is computed based upon the total weight of the organic components and may range from about 2 to 30 parts by weight of ionic surfactant per 100 parts by weight of organic components.
Preferably the polymerization is carried out to complete functionalized diene monomer conversion in order to incorporate essentially all of the polymerizable functional group-bearing monomer. Incremental addition, or a chain transfer agent, may be used in order to avoid excessive gel formation. Such minor modifications are within the skill of the artisan. After the polymerization is complete, the polymer is recovered from a slurry or solution of the polymer. A simple filtration may be adequate to separate polymer from diluent. Other means for separating polymer from diluent may be employed. The polymer may be treated, separately or while slurried in the reaction mixture, in order to separate residues. Such treatment may be with alcohols such as methanol, ethanol, or isopropanol, with acidified alcohols, or with other similar polar liquids. In many cases the polymers are obtained in hydrocarbon solutions and the polymer can be recovered by coagulation with acidified alcohol, e.g., rapidly stirred methanol or isopropanol containing 2% hydrochloric acid. Following this initial coagulation, the polymers may be washed several more times in methanol.
The functionalized diene monomers according to the present invention may also be polymerized with one or more comonomers. Some adjustments in the polymerization recipe or reaction conditions may be necessary to obtain a satisfactory rate of polymer formation, depending on the amount of functionalized monomer included and the other monomers involved. Examples of comonomers that are useful in the practice of this invention are diene monomers such as butadiene, isoprene, and hexadienes. One may, in addition to the diene monomers, use a vinyl monomer such as styrene, xcex1-methylstyrene, divinyl benzene, vinyl chloride, vinyl acetate, vinylidene chloride, methyl methacrylate, ethyl acrylate, vinylpyridine, acrylonitrile, methacrylonitrile, methacrylic acid, itaconic acid and acrylic acid. Mixtures of different functionalized monomers and mixtures of different comonomers may be used. The monomer charge ratio by weight is normally from about 0.10/99.9 to 99.9/0.10 functionalized monomer to comonomer (including any additional vinyl monomer). A charge ratio by weight of about 5/95 to about 80/20 is preferred with 10/90 to 40/60 the most preferred. According to one embodiment, the weight ratio of functionalized diene monomer to diene monomer to vinyl monomer may range from 5:75:20 to 95:5:0. Ratios will vary depending on the amount of chemical functionality desired to be incorporated and on the reactivity ratios of the monomers in the particular polymerization system used.
The polymers containing polar compounds, produced according to this invention, are generally produced as substantially linear polymers having, in general, a number average molecular weight in the range from about 1,000 to a million. The polymer structures from each of the representative monomers, Compounds 1-11, are shown below.
Compounds 1a, 1b, and 1c polymerize to poly[2-(N,N-dimethylaminomethyl)-1,3-butadiene], poly[2-(N,N-diethylaminomethyl)-1,3-butadiene] and poly[2-(N,N-di-n-propylaminomethyl)-1,3-butadiene], respectively. The possible microstructures include: 
for 1a, Rxe2x95x90CH3 
for 1b, Rxe2x95x90CH2CH3 
for 1c, Rxe2x95x90CH2CH2CH3 
Compound 2 polymerizes to poly[2-(cyanomethyl)-1,3-butadiene]. The possible microstructures include: 
Compound 3 polymerizes to poly[2-(aminomethyl)-1,3-butadiene]. The possible microstructures include: 
Compound 4 polymerizes to poly[2-(hydroxymethyl)-1,3-butadiene]. The possible microstructures include: 
Compound 5 polymerizes to poly[2-(carboxymethyl)-1,3-butadiene]. The possible microstructures include: 
Compound 6 polymerizes to poly[2-(acetoxymethyl)-1,3-butadiene. The possible microstructures include: 
Compound 7 polymerizes to poly[2-(2-alkoxy-2-oxoethyl)-1,3-butadiene]. Possible microstructures include: 
Compound 8 polymerizes to poly[2,3-(cyanomethyl)-1,3-butadiene]. The three possible microstructures are: 
Compound 9 polymerizes to poly[2,3-bis(dialkylaminomethyl)-1,3-butadiene]. Possible microstructures include: 
Compound 10 polymerizes to poly[2,3-(ethylbutanoate)butadiene]. 
Compound 11 polymerizes to poly[2,3-bis(3-cyanopropyl)-1,3-butadiene]. Possible microstructures include: 
The homopolymers and copolymers produced according to this invention vary widely in physical and chemical properties, depending on the polar groups employed, the ratio of polar compound to hydrocarbon compound in the product, and the stereochemistry and relative arrangement of polar compound and hydrocarbon units in the polymer chains.
Following crosslinking (thermally or chemically) many of the functionalized polymers of the present invention are elastomeric. When the Tg of the original polymer is below room temperature, the final crosslinked polymer is typically elastomeric. The low glass transition temperatures (Tg) of many of the resulting functionalized polymers herein make these polymers particularly good precursors for elastomers. After crosslinking, i.e., further reaction of the remaining double bonds in the functionalized diene polymer to connect some or all of these bonds between polymer chains, the final material is insoluble in common organic solvents (chloroform, tetrahydrofuran, methylene chloride, acetone, benzene, etc.). This may be accomplished by irradiation with UV light or by vulcanization (addition of sulfur and heating).
Thermoplastic elastomers, actually copolymers of a material with a Tg above room temperature and a polymer with a Tg below room temperature, may also be conveniently formed. For example: 
The higher Tg chain ends serve as the xe2x80x9ccrosslinkersxe2x80x9d and give elastomeric materials. Commercial materials, e.g., spandex, fall into this category.
The polymerized aminomethylbutadienes (1a-1c and 9) can also be quaternized or protonated, if desired, to the salt form (ionic form). 
These materials are useful in various applications such as coatings and membranes, etc. This may be achieved by standard addition of a reagent (CH3I, HCl, etc.) to change the tertiary group to a quaternary group. The nitrogen, for example, will then have four groups attached and a positive charge. This is a salt form that may be completely or partially H2O soluble. Furthermore, if the groups are quaternized about 10-20%, useful ionomers will result. Compounds 1a, 1b, and 1c can be quaternized to produce functionalized ionomers for miscibility enhancement in polymer blends and various other applications.
Other applications include functionalized polyolefin precursors (after hydrogenation of polymers). In the preferred functionalized polymers, the final materials typically contain Cxe2x95x90C bonds. Once hydrogenated, these will become Cxe2x80x94C bonds and thus the final polymers will be polyolefins. The invention therefore provides functionalized polyolefins in one step. The monomers can also be covalently bound modifiers to existing materials.
Adhesive properties also originate from the polymeric functional groups. The aminoisoprenes are quite adhesive, unlike the nonfunctionalized material, polyisoprene. The polymers of this invention are therefore particularly useful in surface coatings and adhesives since the presence of polar groups causes excellent adherence of the coatings to various substrates, such as metals, glasses, and plastics.
The resulting functionalized diene polymers and copolymers are also suitable for the production of numerous molded or extruded manufactured articles such as containers, packaging films, textile fibers, and the like, and for use as rubbers, such as in tires. The incorporation of polar dienes into rubbery hydrocarbon copolymers according to this invention also provides a novel and improved method of functionalization and derivatization.
The physical properties of polymers produced according to this invention vary, depending on the polar compound employed, the proportion thereof in the total polymer, and the method of preparation of the polymer, i.e., whether it is prepared by homopolymerization, random copolymerization or block copolymerization. The polymers may be oily liquids, glassy solids, rubbery solids or highly crystalline polymers.
It is to be understood that the application of the teachings of the present invention to a specific problem or environment will be within the capabilities of one having ordinary skill in the art in light of the teachings contained herein. Examples of the compounds and compositions of the present invention and methods of their preparation and use appear in the following examples.